Chemical deicing is routinely used during the winter season to maintain safer conditions on sidewalks, roads, highways and airports. There are currently numerous materials and compositions used for deicing applications. However, there are many disadvantages to such materials, including their corrosiveness and impact on the environment.
Acetate and formate salts, such as potassium salts, are used in airport runway deicing applications. However, there is evidence that current runway deicing products including potassium acetate and formate cause serious threats to the integrity of the runways and the supporting infrastructure, for example, at major airports. Airport manages are increasingly paying closer attention to how these chemical agent affect the integrity of runways. Any structural decay caused by such chemicals could lead to lost business and, more importantly, could give rise to serious safety issues. Aviation authorities believe that runway deicing products that demonstrate decreased corrosion, carbon brake oxidation, and concrete scaling will warrant a strong market positioning.
Further, compositions with characteristics similar to those of deicing fluids are used as heat transfer fluids in numerous industrial and automotive applications and more prevalently where an operating temperature range beyond that provided by water is desired. For example, such compositions are used as heat transfer fluid compositions otherwise known as antifreeze or coolant when applied in the field of automotive engines. In motor vehicles, heat transfer fluids are used to protect engines from overheating and corrosion. However, by necessity, heat transfer fluids used in motor vehicles are antifreeze liquids to enable cold weather motor vehicle operations.
Examples of frost resistant and anticorrosion coolant compositions are disclosed in U.S. Pat. No. 5,104,562. The compositions contain potassium acetate and potassium formate and may further comprise urea and ethylene glycol. U.S. Pat. No. 6,689,289 B1 discloses compositions of monocarboxylates used as freezing point depressants and corrosion inhibitors in heat transfer fluids.
However, current coolant formulations consist of water, glycol, and small amounts of additives to minimize corrosion and foaming. The most prevalent glycol in heat transfer fluid applications is ethylene glycol occupying 98% of the market space.
However, relatively small amounts of ethylene glycol can cause severe health problems or fatalities if swallowed by people or pets.
Deicers, including those used in airport deicing applications, are dispensed to the surrounding environment. Similarly, about 39% of coolant is disposed of improperly such as onto soil, into public drains and sewer systems, or into open waters. These direct releases into the environment present possible routes of exposure to human, animal and ecological systems. Glycols such as ethylene glycol and propylene glycol used in deicing and heat transfer applications exert a high Biological. Oxygen Demand (BOD) effect on receiving waters and can be detrimental to aquatic species. Biological Oxygen Demand (BOD) is the amount of oxygen required for biological oxidation by bacteria growing under aerobic conditions. Alternatives to glycols have been commercialized for airport deicing applications. However, the heat transfer fluid industries, including industry catering to the motor vehicle antifreeze-coolant market, do not have environmentally friendly, cost competitive alternatives to glycols available for consideration.
Aqueous salt solutions of succinic acid have also been proven to have deicing and heat transfer properties as disclosed in U.S. Pat. No. 6,287,480; U.S. Pat. No. 6,623,57; U.S. Pat. No. 6,635,188; and U.S. Pat. No. 6,846,431. However, such succinate based fluids have not been put to practice due to the high cost of manufacturing from petrochemical feedstocks. Biocatalytic processes such as those using fermentable sugars as a substrate are seen as an economical and environmental alternative to traditional petrochemical processes. More particularly, such processes involving conversion of low value carbohydrates, including some that are considered as waste products, are of increasing interests. For example, calcium magnesium propionate and acetate based road deicers have been produced using a fermentation process as disclosed in U.S. Pat. No. 5,324,442.
Micro-organisms such as E. coli, under anaerobic conditions, produce mixtures of carboxylic acids from fermentable broths as disclosed in J. L. Stokes, “Fermentation of glucose by suspensions of Escherichia coli,” J. Bacteriol., 57:147-158, 1949 and U.S. Pat. No. 6,159,738. The carboxylic acids include succinic, acetic and formic acids. The commercially viable, succinate producing microorganisms described in the literature require neutralization of the fermentation broth to ensure the pH does not become too acidic or too alkaline to kill or inhibit the microbes. Neutralization of the fermentation broth results in the production of salts of succinic acid and other residual carboxylic acids such as acetic and formic.
Thus, there is a need for deicing compositions (in solid or liquid form) and heat transfer fluid compositions that provide a good balance between performance and reduced corrosion and pollution attributes.
There is also a need for a deicing composition (in solid or liquid form) having low corrosion and low BOD useful in deicing various surfaces such as road and runways in cold regions as well as a need for heat transfer fluid compositions having a lower BOD effect.
There is further a need for providing a biobased carboxylate salts deicing composition which is economically attractive for use as a commercial deicer, particularly at airports. A similar need exists for making biobased carboxylate salts economically attractive for use as a commercial heat transfer fluid.